Histone deacetylase inhibitors sensitize glioblastoma cells to TRAIL-induced apoptosis by c-myc-mediated downregulation of cFLIP

作者：Bangert A; Cristofanon S; Eckhardt I; Abhari B A; Kolodziej S; Haecker S; Vellanki S H K; Lausen J; Debatin K M; Fulda S^*

来源：Oncogene, 2012, 31(44): 4677-4688.

DOI：10.1038/onc.2011.614

• apoptosis
• TRAIL
• glioblastoma
• HDACI
• cFLIP

Glioblastoma is the most common primary brain tumor with a very poor prognosis, calling for novel treatment strategies. Here, we provide first evidence that histone deacetylase inhibitors (HDACI) prime glioblastoma cells for tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) -induced apoptosis at least in part by c-myc-mediated downregulation of cellular FLICE-inhibitory protein (cFLIP). Pretreatment with distinct HDACI (MS275, suberoylanilide hydroxamic acid, valproic acid) significantly enhances TRAIL-induced apoptosis in several glioblastoma cell lines. Monitoring a panel of apoptosis-regulatory proteins revealed that MS275 reduces the expression of cFLIP(L) and cFLIP(S). This leads to decreased recruitment of cFLIP(L) and cFLIP(S) and increased activation of caspase-8 to the TRAIL death-inducing signaling complex, resulting in enhanced cleavage of caspase-8, -9 and -3 and caspase-dependent apoptosis. Also, MS275 promotes TRAIL-triggered processing of Bid, activation of Bax, loss of mitochondrial membrane potential and release of cytochrome c. MS275-mediated downregulation of cFLIP occurs at the mRNA level independent of proteasome-or caspase-mediated degradation, and is preceded by upregulation of nuclear levels of c-myc, a transcriptional repressor of cFLIP. Notably, MS275 causes increased binding of c-myc to the cFLIP promoter and reduces cFLIP promoter activity. Indeed, knockdown of c-myc partially rescues cFLIP(L) from MS275-inferred downregulation and significantly decreases TRAIL-and MS275-induced apoptosis. Also, overexpression of cFLIP(L) or cFLIP(S) significantly reduces MS275- and TRAIL-induced apoptosis. Importantly, MS275 sensitizes primary cultured glioblastoma cells towards TRAIL and cooperates with TRAIL to reduce long-term clonogenic survival of glioblastoma cells and to suppress glioblastoma growth in vivo underscoring the clinical relevance of this approach. Thus, these findings demonstrate that HDACI represent a promising strategy to prime glioblastoma for TRAIL-induced apoptosis by targeting cFLIP.

• 出版日期2012-11